Sugar Aeration Clarifier

ABSTRACT

Device for clarifying sugar syrup from a sugared juice, such as raw juice from sugar cane or from sugar beet, containing sugar and impurities. The device includes the sub-systems for facilitating coagulation and flocculation of the sugar syrup in order to obtain a clarified syrup, aeration filtration of the sugar syrup in order to obtain a retentate (mud) and a filtrate (clarified syrup), concentration of the retentate at the surface of the sugar syrup, further concentration of retentate during its removal from the sugar syrup surface, steps and device in order to obtain clarified syrup and mud in order that they are both subjected to further sugar mill refining operations.

This application claims priority to Provisional Application No.61/146,955 filed on Jan. 23, 2009.

The subject of the present invention is a device for producing clarifiedsugar syrup from sugared juice, such as a raw juice from sugar cane orfrom sugar beet.

At present, the production of sugar (or white sugar) from sugar canecomprises a certain number of treatments implemented in a sugar mill,followed by a certain number of supplementary treatments implemented ina refinery.

Schematically, the principal treatment steps in the sugar mill are theextraction of the sugar by crushing—pressing of the cane or by diffusionwhich leads to a raw sugared juice, the clarification of this juice byaddition of lime, neutralization of the latter by carbon dioxide (in thecase of sugar beet) or acids and decantation of the thus treated juice,the concentration of the resulting juice and finally the crystallizationand spinning of the sugar generally in three steps, which leads to rawsugar and molasses being obtained. In the refinery, the operations towhich the raw sugar is subjected are essentially a fining (washing ofthe crystals with a saturated aqueous sugar solution then spinning) inorder to eliminate the impurities situated on the surface of thecrystals, re-dissolving of the resulting sugar, a further clarificationstep, a decolorization, a crystallization and a spinning. Because of therelatively high purity of the syrup which is subjected to thiscrystallization, the latter operation is more difficult than in thesugar mill and requires two to three crystallization/separation steps,the purity of the run-off from the last crystallization/separation stepis still very high and the sugar which it contains is extracted by acomplementary crystallization of 3 or 4 steps, termed crystallization“of low grade sugars”, which leads to the production of a very coloredsugar, which is recycled at the head of the refinery, and of molasses.It will be noted that because of the high viscosity of the productsubjected to this crystallization, the latter is costly in material andin energy.

For several years, a certain number of methods and devices have beenstudied in order to improve the quality of the sugar at the level of thesugar mill.

Thus, Kwock et al. proposed, in the U.S. Pat. No. 5,554,227, a methodleading to the production of a raw sugar with low coloration termed SVLC“Super Very Low Color” by linking the operations of filtration over amembrane, of softening and of crystallization. This method permits asimplification of the refining of the raw sugar and in particular theelimination of the operations of fining and purification. It permitslikewise the implementation of a chromatography step in order to recoverthe sugar from the molasses and thus to improve the extraction yield ofthe sugar mill. This chromatography generally leads to the production oftwo fractions, i.e. an extract rich in sugar and a raffinate containingthe impurities from the sugar.

McKearny et al. proposed for their part, in the internationalapplication WO 95/16 794, chromatography as a means of purification ofthe juices from sugar beet after their clarification, softening andconcentration and before crystallization. This document shows that,starting from syrup with purity (percentage by weight of sugar withrespect to the dry material) of approximately 90%, chromatographypermits this purity to be raised to at least 94%. The crystallization ofsuch syrup in three crystallization/separation steps gives a white sugarand molasses with a purity of approximately 60%.

However, the application of this method to sugar cane juice isinconceivable from an economic point of view.

In fact the production of white sugar from sugar cane juice requiresstarting from a syrup having a purity which is much higher than that ofa sugar beet syrup, i.e. of the order of 98% instead of 94%. In theseconditions, it becomes impossible to produce white sugar with a goodyield by means of crystallization with 3 crystallization/separationsteps because, in order to preserve the quality of the produced sugar,it is not possible to crystallize more than 50 to 60% of the sugarpresent, at each crystallization/separation step.

One solution to this problem would be to prolong the crystallization by2 or 3 crystallization/separation steps termed depletion steps, whichcomes to reproducing crystallization of low grade products implementedin the refinery, and the avoidance of which is precisely what is beingsought.

The object of the present invention is therefore to resolve theaforementioned problem in an economical manner and in order to do this aproduction device for refined sugar (or white sugar) is proposedstarting from a sugared juice, such as raw juice from sugar cane or fromsugar beet, containing sugars and impurities, this device beingcharacterized in that it comprises the operations of:

The starting material used in this device is the sugar syrupconcentrated from raw sugar cane juice, for example obtained bycrushing—pressing of the sugar canes, which leads to a fibrous residue(bagasse) and a raw juice; as a variation, recourse can be had to thediffusion technique comprising depleting the sugar canes, cut intofragments, by hot water, which leads to a residue and to a raw juice. Itgoes without saying that the raw starting syrup could likewise be a rawjuice from sugar beet.

The aforementioned concentrated raw sugar syrup, which contains sugarsand non-sugars is subjected to a process using the “sugar aerationclarifier” device consisting of:

an intermediate continuous flow reaction of the sugared syrup passingthrough an enclosed pipe chamber (flocculator) for a holding period of 5to 120 seconds in order to facilitate chemical coagulation andflocculation of the sugared syrup contaminant particle's agglomeration;

aeration of the sugared syrup within the flocculator from a regenerativeturbine pump recirculation system to further agglomerate the particlesin order to begin formation of a retentate and a filtrate;

the invention furthermore passes the aerated sugared syrup from theflocculator into the vessel where it is evenly distributed by means ofan inlet distribution box;

separation of the retentate from the filtrate by means of passing theaerated sugar syrup through a corrugated plate separator composed ofmultiple plates angled at 55-65 degrees which facilitate laminar flowconditions as well as provide a separation surface for the agglomeratingretentate particles;

concentration of the retentate (mud) at the surface of the sugar syrupwithin the vessel in order to obtain a floating skimmable mud;

further concentration of the retentate (mud) by means of a chain andpaddle skimmer system moving across the syrup surface and up an inclinedplane such that any filtrate (clarified syrup) returns to the vessel andthe thickened mud is removed to the hopper for further mill processing;

and final extraction of the clarified syrup filtrate from the vesselthrough effluent collection pipe weirs for further mill processing.

Thus, in accordance with the present invention there is a removal ofimpurities and decolorization of the sugar syrup by the “sugar aerationclarifier” step following the mill sugar juice concentration operation.

Advantageously, the device according to the invention comprisesfurthermore a clarification operation of the sugared juice before it issubjected to the further process operation; this clarificationeliminates the non-dissolved materials.

There is therefore reduced production of molasses at later processingsteps within the mill, the non-sugars (impurities) from the sugaredsyrup being eliminated and the clarified syrup being recovered in theextract fraction of said device, which increases the global yield.

The device according to the invention is furthermore operated on acontinuous flow basis within an operating temperature of 135F to 190 F.

The device according to the invention is furthermore operated on acontinuous flow basis with an aeration recirculation system using aregenerative turbine pump discharge pressure of 20-100 psi fed withsugar syrup from the effluent box mixed with either ambient air orcompressed air, according to operator preference. Additionally, theaeration recirculation system generates 20-30 micron bubbles at a gassaturation rate 6-10% by volume of re-circulated sugar syrup. The sugarsyrup is re-circulated at a rate of 10-50% of the sugar aerationclarifier influent feed rate.

The device according to the invention is furthermore operated with atotal retention time of 10 to 30 minutes.

The device according to the invention furthermore floats the retentateto the surface of the vessel whereby it is concentrated and skimmed bypushing it up an inclined plane of 30-50 degrees pitch with a chain andpaddle system. The collected mud is then dropped into a hopper forremoval to further mill processing.

The device according to the invention furthermore passes the clarifiedsyrup out of the vessel through effluent weir piping.

The device according to the invention can furthermore comprise adecolorization operation of the filtrate, before it is subjected to thelater crystallization operation; this decolorization is captured withinthe retentate mud.

One embodiment of the present invention is described hereafter withreference to the attached single DRAWING which is a schematicrepresentation of the device according to the invention.

A BRIEF DESCRIPTION OF THE DRAWING illustrates the object of the “sugaraeration clarifier” clarification process is to eliminate the majorportion of the impurities and/or suspended solid materials in the sugarsyrup. The DRAWING includes several views of the “sugar aerationclarifier”. The FRONT VIEW illustrates the common components visiblefrom that perspective. The SIDE VIEW illustrates the common componentsvisible from that perspective, as well as cut-away internal views of theCorrugated Plate Separator and the Collection Pipe Weir components forfurther clarity. The BACK VIEW illustrates the common components visiblefrom that perspective, as well as cut-away internal views of theCorrugated Plate Separator and the Inlet Distribution Box components forfurther clarity. Additionally, the BACK VIEW has a captioned DETAIL (4)more closely illustrating the Inlet Distribution Box. The PLAN VIEWillustrates the common components visible from that perspective.Additionally, the PLAN VIEW has a captioned DETAIL (7) more closelyillustrating the Chain & Paddle System. For this purpose, the raw juiceis supplied directly from the mill sugar juice concentrator (or anintermediate holding tank) to the “sugar aeration clarifier” as a sugarsyrup to the feed inlet (1 FRONT VIEW) after having been heatedpreferably to 135-190F degree, for example by means of an indirect heatexchanger. In the flocculator (2 FRONT VIEW), it is mixed under briskagitation with or without dosed chemistry for a continuous flow holdingperiod of 5 to 120 seconds, the chemistry supplied to the latter in astaged injection process at multiple points (3 FRONT VIEW) along theflocculator (2 FRONT VIEW).

The sugar syrup is then directed into and evenly distributed within thevessel (6 PLAN VIEW) by means of an inlet distribution box (4 BACK VIEWand captioned DETAIL 4). The sugar syrup then passes in a“cross-counter” flow manner through a corrugated plate separator (5FRONT VIEW and BACK VIEW) angled at 55-65 degrees which facilitateslaminar flow conditions as well as provides a separation surface for theagglomerating retentate particles to further form. “Cross-counter” isdefined as the syrup flowing across the vessel (6 PLAN VIEW) anddownward towards the filtrate collection pipe weirs (10 SIDE VIEW) whilethe agglomerated retentate particles float upward in the counterdirection toward the surface, thus a “cross-counter” flow.

The agglomerated retentate particles mixed with air float to the surfaceof the vessel (6 PLAN VIEW) where they are concentrated and skimmed bymeans of a chain and paddle system (7 PLAN VIEW and captioned DETAIL 7),the agglomerated particles are thickened as they are moved up theinclined plane (8 PLAN VIEW), with the clarified syrup filtrate drainingback to the vessel (6 PLAN VIEW). The retentate (mud) is removed forfurther mill processing to a hopper (9 SIDE VIEW) at the top andadjacent to the inclined plane (8 PLAN VIEW).

The clarified syrup filtrate is then directed into and passes throughcollection pipe weirs (10 SIDE VIEW) and further flows up to an effluentbox (11 SIDE VIEW) or “clear well”. From the effluent box (11 SIDE VIEW)a 10 to 50 percent portion of the clarified syrup is recirculated backto the flocculator (2 FRONT VIEW) through the aeration system (12 FRONTVIEW and SIDE VIEW) with a regenerative turbine pump. Alternatively aninjection point at the side of the vessel could be used for the aerationrecirculation return. The remaining clarified syrup is removed from theeffluent box (11 SIDE VIEW) via an overflow outlet (13 BACK VIEW), oralternatively a pump.

Rentate solids having a density such that they sink to the bottom of thevessel (6 PLAN VIEW) rather than float for skimming by the chain andpaddle system (7 PLAN VIEW and captioned DETAIL 7) may be removed via adrain (14 FRONT VIEW) located at the bottom of the vessel (6 PLAN VIEW).

Thus the clarified and decolored sugar syrup filtrate is then suppliedto the mill for further processing.

And the retentate “mud”, is supplied to the mill for furtherreprocessing.

In addition, with respect to a conventional sugar mill, the deviceaccording to the invention permits an extraction yield of the sugarcalculated at the entry to the crystallization workshop which goes toover 99%.

1. Device for producing clarified sugar syrup from sugared juice, suchas raw juice from sugar cane or from sugar beet, containing sugar andimpurities, which comprises the operations of coagulation andflocculation of the sugared syrup in order to obtain a clarifiedfiltrate, aeration filtration of the sugared syrup in order to obtain aretentate (mud) and a filtrate (clarified syrup), concentration anddewatering of the retentate, steps in order to obtain filtrate andretenate in order that they may both subjected to further independentsugar mill refining operations.
 2. Device according to claim 1,characterized in that it comprises furthermore an enclosed pipe chamber,the “flocculator” for the facilitating an intermediate continuous flowreaction process resulting from the addition of organic and/or inorganicchemical coagulants and flocculants, such as cationic polymer,phosphoric acid, lime, and anionic polymer, as a pretreatment operationfor aiding the removal of impurities and decolorization of the filtratewhen it is subjected to the sugar aeration clarification operation. 3.Device according to claim 1, characterized in that it comprisesfurthermore an aeration filtration operation utilizing a regenerativeturbine pump recirculation system.
 4. Device according to claim 1,characterized in that it comprises furthermore a concentration operationof the extracted retentate or “mud”.
 5. Device according to claim 1,characterized in that it comprises: a sugar aeration clarifier featuringa flotation vessel, a means of evenly distributing the influent sugarsyrup, a means of separating the agglomerated particles from theclarified sugar syrup by passing the solution through a separator platepack assembly, a means of aerating and floating the agglomerated solidretentate particles to the surface of the vessel for collection, a meansof sweeping the agglomerated solids up an inclined surface, a means ofcollecting the solids in a hopper basin for transfer to further millprocesses, a means of extracting the clarified sugar syrup filtrate fromthe vessel with adjustable effluent weirs for further mill processes.